# Static friction on banked curve

1. Feb 25, 2012

### runner2392

If a curve with a radius of 89.0m is perfectly banked for a car traveling 71.0km/hr, what is the minimum coefficient of static friction for a car not to skid when traveling at 91.8km/hr?

I figured out theta = 24. 03degs from the equations F(normal)*cos(theta) = mg and F(normal)*sin(theta) = m(v^2/r).

Then to find mus, I tried: m(v^2/r) = F(normal)sin(theta) -F(static f). For F(normal) I substituted mg/cos(theta) but ultimately I got the incorrect answer. Can someone please help?
Thanks

2. Feb 26, 2012

### ehild

Make a drawing and show your work in detail, please. The static friction acts along the load: It contributes with its horizontal component to the centripetal force, and its vertical component has to be taken into account in the equation for the vertical force components.

ehild

3. Feb 26, 2012

### runner2392

4. Feb 26, 2012

### ehild

How did you calculate with the friction?

ehild

5. Feb 26, 2012

### runner2392

figured it out

Last edited: Feb 26, 2012